1. Field of the Invention
The present invention relates to a facsimile apparatus, and more particularly, to a facsimile apparatus comprising an image recovery circuit for recovering image data of multi-gradation stages including an image density of half-tone (referred to as a multi-value image data hereinafter) from pseudo half-tone binary image data. Further, the present invention relates to an image processing apparatus, and more particularly, to an image processing apparatus comprising a judgment circuit for judging whether inputted binary image data are either binary image data of pseudo half-tone image or binary image data of non-half-tone image, and further comprising an image recovery circuit for recovering multi-value image data from inputted binary image data of pseudo half-tone image.
2. Description of the Related Art
In a conventional facsimile apparatus, in order to transmit an image signal through a public telephone line, a transmitter converts a half-tone image such as a photograph image or the like into binary image data of pseudo half-tone image by binarizing them using a dither method or the like, and then, transmits the converted image data to a receiver of the other party. On the other hand, the receiver recovers multi-value image data from the received binary image data of pseudo half-tone.
Further, recently, there has been put into practice a color laser printer for recording an image of multi-value image data at a high speed and with a high resolution, however, there have been widely used binary printers for recording binary image data, generally. In order to store multi-value image data in a storage unit, it is necessary to provide the storage unit having a relatively large capacity.
In order to solve the above problem, the following method is suggested. In this method, the multi-value image data are converted into binary image data, and then, the converted binary image data are stored in the storage unit. Furthermore, upon processing the binary image data or recording the binary image data, after reading out the above binary image data from the storage unit, multi-value image data are recovered from the read binary image data.
The method and apparatus of this type are disclosed in the Japanese patent laid-open publications Nos. 62-114378 and 62-107573.
The image processing method disclosed in the former publication (referred to as a third conventional method hereinafter) includes the following steps, in order to make a multi-value printer give full scope to its unit performance by printing out an image using the multi-value printer even in response to binary image data, or in order to improve the quality of recovered character image:
(a) recovering a half-tone image from the inputted binary image data; and PA1 (b) performing predetermined processes such as a magnification and reduction process, an image emphasis process or the like for the recovered half-tone image. In the third conventional method, in order to recover multi-value image data from binary image data, a window in a square shape having a predetermined size is provided close to a specified pixel to be recovered or to be processed, and then, a smoothing process is performed for the inputted image data within the provided window. PA1 (a) dividing means for dividing binarized image information into predetermined blocks; PA1 (b) judging means for judging the image tone by each block; and PA1 (c) converting means for converting the binarized image information within the block into multi-value image data according to the judgment result thereof. In the fourth conventional apparatus, upon transmitting image data and storing them, there are used binary image data so as to display and edit them more efficiently. Further, upon reproducing the image, there is used a multi-value representation close to an analogue image. Concretely, the judgment means is constituted by an image judgment table ROM for judging the image tone using a pattern matching method within each block corresponding to a size of a dither matrix, and the converting means is constituted by a conversion ROM. PA1 (a) a process for extracting each kind of binary image data; PA1 (b) a process for switching over the method for converting the pixel density thereof; and PA1 (c) a process for switching over the decoding method such as the method for compressing image data or the like. PA1 (a) setting a mask for surrounding a plurality of pixels including a specified pixel; PA1 (b) taking out a pixel pattern formed based on values of a plurality of pixels within the mask; PA1 (c) generating an image area signal corresponding to the above-mentioned pixel pattern according to a table of image area signals on the pixel patterns previously stored in a storage unit dividing all the pixel patterns which may be caused into the dot photograph area and the document area; and PA1 (d) outputting the generated image area signal as the image area signal corresponding to the specified pixel. Concretely, the respective pixel patterns are previously stored in a table ROM by dividing the pixel pattern into the dot photograph area and the document area, and when an image signal to be processed is inputted to an address terminal of the table ROM, resulting in the image area signal in the data terminal of the table ROM. PA1 image data receiving means for receiving image data transmitted from a transmission apparatus apart from said facsimile apparatus; PA1 converting means for converting binary image data representing an image density of each pixel in binary representation of black pixel or white pixel, into multi-value image data representing an image density of each pixel in multi-gradation stages representation including half-tone density; PA1 printing means for printing an image corresponding to image data on a paper; PA1 discrimination signal receiving means for receiving a discrimination signal transmitted from said transmission apparatus; PA1 judging means for judging whether said image data received by said image data receiving means are either simple binary image data binarized using one threshold value or pseudo half-tone image data including half-tone information binarized using a plurality of threshold values, based on said discrimination signal received by said discrimination signal receiving means; and PA1 controlling means for controlling said converting means and said printing means to convert image data judged as said pseudo half-tone image data by said judging means into multi-value image data, and print an image corresponding to said converted multi-value image data, and for controlling said printing means to print an image corresponding to image data judged as said simple binary image data by said judging means without converting said simple image data into multi-value image data. PA1 image reading means for optically reading a density of a document image by respective fine pixels and outputting image data corresponding to said read document image; PA1 simple binarizing means for binarizing image data outputted from said image reading means using one threshold value and outputting simple binary image data; PA1 pseudo half-tone binarizing means for binarizing image data outputted from said image reading means using a plurality of threshold values and outputting pseudo half-tone image data including half-tone information; PA1 selecting means for selecting one of said simple binary image data outputted from said simple binarizing means and said pseudo half-tone image data outputted from said pseudo half-tone binarizing means and outputting said selected image data; and PA1 transmitting means for transmitting said image data selected by said selecting means and transmitting a predetermined discrimination signal corresponding to said image data selected by said selecting means, PA1 said receiving means comprising: PA1 receiving means for receiving said image data and said predetermined discrimination signal transmitted from said transmitting means of said transmission apparatus; PA1 judging means for judging whether said image data received by said receiving means are either said simple binary image data or said pseudo half-tone image data based on said predetermined discrimination signal received by said receiving means; PA1 converting means for converting said image data received by said receiving means into multi-value image data representing an image density of each pixel in multi-gradation stages representation including half-tone density when said judging means judges that said image data received by said receiving means are said pseudo half-tone image data; and PA1 printing means for printing an image corresponding to said multi-value image data converted by said converting means on a paper when said judging means judges that said image data received by said receiving means are said pseudo half-tone image data, and for printing an image corresponding to said image data received by said receiving means on a paper when said judging means judges that said image data received by said receiving means are said simple binary image data. PA1 receiving means for receiving binary image data and a recovery control signal transmitted from a further facsimile apparatus of the other party; PA1 first recovery means for performing a first recovery process for recovering multi-value image data from said binary image data binarized using a first pseudo half-tone binarizing method; PA1 second recovery means for performing a second recovery process for recovering multi-value image data from said binary image data binarized using a second pseudo half-tone binarizing method different from said first pseudo half-tone binarizing method; and PA1 controlling means for controlling said first and second recovery means to selectively perform one of said first and second recovery processes for said binary image data received by said receiving means, based on said recovery control signal received by said receiving means. PA1 counting means for counting a number of adjacent points, in each of which the same kinds of two pixels are adjacent to each other, within a block area composed of a plurality of pixels having a specified pixel to be processed, based on inputted binary image data including first binary image data binarized using a pseudo half-tone binarizing method with a plurality of predetermined binarizing threshold values and second binary image data binarized using a non-half-tone binarizing method with a predetermined binarizing threshold value; PA1 judging means for judging whether said inputted binary image data are either first or second binary image data by comparing said the number of adjacent points counted by said counting means with a predetermined judgment threshold value, and outputting a judgment result thereof; and PA1 controlling means for altering said predetermined judgment threshold value based on a resolution of said inputted binary image data.
Further, the image processing apparatus disclosed in the latter publication (referred to as a fourth conventional apparatus hereinafter) comprises the following means, in order to prevent the quality of image from deteriorating in the case of using a binarizing circuit having a simple structure using a dither method or the like, and also in order to constitute the image processing apparatus with simple circuits:
However, in the third conventional method, when setting a larger window, a blurring or shaded-off portion may be reproduced in the reproduced image. On the other hand, when setting a smaller window, a so-called Moire may be caused, resulting in deterioration of the reproductivity of the image.
Further, in the fourth conventional apparatus, since the image tone is judged by each block corresponding to the size of the dither matrix, the image tone can not be judged when the dither matrix of the binarizing circuit is not known, and also the image tone can not be judged when the image data to be judged are binarized using the other pseudo half-tone binarizing method.
For example, in the case where a document image to be transmitted from a facsimile apparatus of a transmission side is a character image, when another facsimile apparatus of a receiving side recovers multi-value image data from received binary image data using the third conventional method and the fourth conventional apparatus, an image recorded in another facsimile apparatus of the receiving side may be different from the original document image at the transmission side, and then, the reproductivity of the image is lowered, resulting in deterioration in the recorded image.
Further, generally speaking, in binary image data binarized using the pseudo half-tone binarizing method, there are mixedly both spatial frequency components of a texture of a pseudo half-tone and spatial frequency components of an original image itself, wherein the frequency of the former components is higher than the frequency of the latter components. However, when the resolution upon reading an image becomes lower, a difference between bands of both the spatial frequency components becomes smaller, and finally the difference therebetween becomes substantially zero. In this case, when recovering multi-value image data from such binary image data, a texture component is also recovered together with the components of the original image, and then, the reproductivity of the image is lowered, resulting in deterioration in the recorded image.
In the case of recovering multi-value image data such as image data of a photograph image from binary image data binarized using the pseudo half-tone binarizing method in the above-mentioned third conventional method and fourth conventional apparatus, there are used spatial filters each having a predetermined size as described above. In this case, generally speaking, the size of the spatial filter is determined taking into consideration not only the spatial frequency band of the texture of the pseudo half-tone image to be removed but also the spatial frequency band of the original image itself to be stored or to be emphasized. However, in the case of recovering multi-value image data using a spatial filter having a fixedly predetermined size, when the resolution of the binary image data is changed, the spatial frequency band of the latter original image moves, and then, the original image data can not be recovered, resulting in lowering the reproductivity of the recovered image.
As described above, in binary image data binarized using the pseudo half-tone binarizing method, there are mixedly both the spatial frequency components of the texture of the pseudo half-tone image and the spatial frequency components of the original image itself. Generally, the spatial frequency of the former is higher than the spatial frequency of the latter, however, in particular, the spatial frequency band of the binary image data binarized using a Fattening type ordered dither method of the pseudo half-tone binarizing method is lower than that of the former.
Therefore, in the case where there is almost no difference between the spatial frequency bands of both ones, an image area judgment circuit for only judging whether inputted image data are binary image data binarized using the pseudo half-tone binarizing method or binary image data of non-half-tone image may misjudge of the image area judgment. If the apparatus of the third conventional method and the conventional fourth apparatus recover multi-value image data from binary image data based on the results of the misjudged image area judgment, it can not recover the original image, resulting in lowering the reproductivity of the image.
Further, in a conventional facsimile apparatus, in order to transmit an image signal through a public telephone line, a transmitter converts image data of non-half-tone image such as characters into binary image data of non-half-tone image by binarizing them using a predetermined threshold value and then transmits the converted binary image data to a receiver of the other party, and also the transmitter converts multi-value image data of half-tone-image into binary image data of pseudo half-tone image by binarizing them using a dither method and then transmits the converted binary image data to the receiver of the other party. It is to be noted that the multi-value image data means image data of multi-gradation stages in the specification. On the other hand, the receiver of the other party performs different processes depending on the kind of the image of the received image data such as non-half-tone image, pseudo half-tone image or the like. Namely, it is necessary for the receiver to perform the following processes:
Therefore, it is necessary to automatically judge whether or not the received image data are binary image data of non-half-tone image or binary image data of pseudo half-tone image, and there is disclosed in the Japanese Patent examined publication No. 63-11832, a method for judging the kind of the received image data and generating an image area signal having the judgment result (referred to as a fifth conventional method hereinafter). The fifth conventional method is provided for judging whether or not respective pixels of an image signal having both of a dot photograph area and a document area of characters are included in the dot photograph area or the document area, and for generating an image area signal for representing the judged image area. The fifth conventional method includes the following steps:
Further, there is suggested in Yoshinobu MITA et al, "Higher fine multi-value recovery of binary image by Neural Network", Japan Hard copy, '90, NIP-24, pp233 through 236, 1990, an apparatus for automatically judging whether or not inputted binary image data are binary image data of non-half-tone image or binary image data of pseudo half-tone image (referred to as a sixth conventional apparatus hereinafter). In the sixth conventional apparatus, by using a back propagation method for Neural Network, there is performed not only a process for converting inputted binary image data into multi-value image data using a Neural Network but also a process for dividing inputted binary image data into predetermined kinds of image area and for converting them into multi-value image data depending on the divided image area using the Neural Network. The Neural Network of the sixth conventional apparatus has a three-layer structure comprising an input layer, an intermediate layer and an output layer. In the input layer, there are provided a number of units corresponding to a number of pixels included in a window provided close to a specified pixel, and there is provided in the output layer one unit for outputting multi-value image data.
However, in the fifth conventional method, since there is provided the pixel pattern table ROM for judging image areas, as the area to be judged for area judgment increases, the manufacturing cost thereof increases. Further, in the sixth conventional apparatus, the composition of the apparatus is complicated, and the processing speed is extremely low.